DE102019129789A1 - Process for depositing a two-dimensional layer and CVD reactor - Google Patents

Abstract

The invention relates to a method and a device for depositing a two-dimensional layer on a substrate (4) in a CVD reactor (1), in which a process gas is fed into a gas distribution chamber (11, 21) of a gas inlet element by means of a feed line (10, 20) (2) is fed, which has gas outlet openings (14, 24) which open into a process chamber (3) in which the process gas or decomposition products of the process gas in the process chamber (3) are brought to a surface of a substrate (4), and in which the substrate (4) is brought to a process temperature (TP) by means of a heating device (6), so that the process gas in the process chamber reacts chemically in such a way that the two-dimensional layer is deposited on the surface. In order to separate heterostructures, it is proposed that the gas inlet element (2) have at least two separate gas distribution chambers (11, 21), each of which is supplied with a supply line (10, 20) with different gases or gas mixtures, which simultaneously come from the different , in each case one of the gas distribution chambers (11, 21) associated with gas outlet openings (14, 24) emerge.

Description

Field of technology

The invention relates to a method for depositing a two-dimensional layer on a substrate in a CVD reactor, in which a process gas is fed into a gas distribution chamber of a gas inlet element by means of a feed line, which process gas has gas outlet openings which open into a process chamber in which the process gas or decomposition products of the process gas in the process chamber are brought to a surface of a substrate, and in which the substrate is brought to a process temperature by means of a heating device, so that the process gas in the process chamber reacts chemically in such a way that the two-dimensional layer is deposited on the surface.

The invention also relates to a device for depositing a two-dimensional layer on a substrate with a CVD reactor which has a gas inlet element with a supply line opening into a gas distribution chamber, a process chamber into which the gas outlet openings of the gas distribution chambers open, and a susceptor that can be heated by a heating device of the substrate, the feed line being connected to a gas mixing system in which at least one inert gas source and at least one reactive gas source a reactive gas, which has the property of being brought into a heated process chamber to react chemically in such a way that at least one inert gas source Substrate a two-dimensional layer is deposited, are provided.

The invention also relates to the use of a CVD reactor for depositing a two-dimensional layer on a substrate.

State of the art

The DE 10 2013 111 791 A1 describes the deposition of two-dimensional layers using a CVD reactor in which the gas inlet element is a showerhead. The deposition of graphene with a CVD reactor, in which a showerhead is used as a gas inlet element, is from the WO 2017/029470 A1 known. CVD reactors are known from the DE 10 2011 056 589 A1 , DE 10 2010 016 471 A1 as DE 10 2004 007 984 A1 .

The WO 2014/066100 A1 describes a showerhead with a gas outlet surface that has two gas outlet zones.

The US 2010/119727 describes a showerhead with several gas distribution chambers arranged one above the other.

Summary of the invention

The invention is based on the object of specifying a CVD reactor with which a plurality of mutually different two-dimensional layers can be deposited on top of one another, and of specifying a method in this regard.

The object is achieved by the invention specified in the claims, the subclaims not only representing advantageous developments, but also independent solutions to the object.

A CVD reactor according to the invention has two volumes which are separated from one another and which each form a gas distribution chamber. A first process gas can be fed into a first gas distribution chamber. The process gas can be a gas mixture of several, for example two, reactive gases. The process gas can preferably only be a reactive gas. This first reactive gas can be used to deposit a first two-dimensional layer. The second gas distribution chamber is designed so that a second process gas can be fed into it in order to deposit a second two-dimensional layer. The second process gas is different from the first process gas and can consist of one or more reactive gases. However, the second process gas can preferably consist of only one reactive gas. When depositing multilayer structures, a different process gas, in particular only one reactive gas or a mixture of several, in particular two, reactive gases is fed one after the other into one and the other gas distribution chamber. A process gas is preferably always fed into only one of the several gas distribution chambers. An inert gas, for example a noble gas, is fed into the other of the plurality of gas distribution chambers. In the method according to the invention, the gas inlet element has at least two gas distribution chambers which are separate from one another and which are each supplied with a supply line with gases or gas mixtures which differ from one another. However, the device can also have more than two gas distribution chambers, each of which can be fed with a supply line. The gases emerge simultaneously from different gas outlet openings, each assigned to one of the gas distribution chambers. A CVD reactor according to the invention can have gas distribution chambers which are arranged vertically one above the other and which can each extend over the entire gas outlet surface of the gas inlet element. The The gas outlet surface can have a circular disk shape and evenly distributed gas outlet openings. The gas outlet openings are connected to the various gas distribution chambers, one opening in each case being flow-connected to only one gas distribution chamber. The process gas can flow through the gas outlet openings into the process chamber of the CVD reactor, where it reacts chemically in such a way that a two-dimensional layer is deposited on the surface of a substrate, which can be a sapphire substrate, a silicon substrate or the like. Each gas distribution chamber is flow-connected to the gas outlet surface by a multiplicity of gas outlet openings, the gas outlet openings being arranged essentially evenly distributed over the gas outlet surface. According to a first variant of the invention, an inert gas is fed into a first of the gas distribution chambers and a reactive gas is fed into a second of the gas distribution chambers, which reactive gas is pyrolytically decomposed in the process chamber, the decomposition products forming a two-dimensional layer on the substrate. In a second alternative of the invention, a different reactive gas can be fed into each of the gas distribution chambers. In the process chamber, the reactive gases can chemically react with one another and form a two-dimensional layer. In the first alternative, preference is given to depositing graphene or hBN, with methane or borazine being used as the reactive gas. In the second alternative of the method, a gas of a transition metal, for example tungsten, molybdenum or the like, can be fed into one of the gas distribution chambers. A gas of the sixth main group, for example sulfur, selenium or tellurium, can be fed into the second gas distribution chamber. The two-dimensional layers can be transition metal chalcogenides. In a preferred embodiment, the CVD reactor has a gas outlet plate facing the process chamber, which on its rear side adjoins a cooling chamber through which a cooling medium can flow. A first gas distribution chamber into which a first gas is fed can be located above the cooling chamber. The gas distribution chamber is connected to the gas outlet surface of the gas outlet plate of the gas inlet element with tubes that cross the cooling chamber. First tubes alternate with second tubes in the lateral direction, the first tubes connecting the first gas distribution chamber to the gas outlet surface and the second tubes crossing both the cooling chamber and the first gas distribution chamber and connecting a second gas distribution chamber arranged above the first gas distribution chamber to the gas outlet plate . However, the gas outlet element can also have a configuration as shown in FIG DE 10 2013 101 534 A1 , DE 10 2009 043 840 A1 or DE 10 2007 026 349 A1 is described. The content of these documents is therefore fully included in the disclosure content of this application. The bottom of the process chamber is formed by a susceptor, which can be heated to a process temperature of preferably over 1000 ° C. with a heating device. According to a further alternative, a mixture of reactive gases can also be fed into one of the gas distribution chambers, for example for the deposition of tungsten sulfide. The gas mixture can consist of tungsten hexacarbonyl W (Co) ₆ and di-tert-butyl polysulfide. In one embodiment, a multilayer structure is deposited on a sapphire substrate, the multilayer structure consisting of at least one layer of hexagonal boron nitride (hBN), which is, for example, 5 nm thick. A graphene layer or several graphene layers can be deposited on top of one another. On the graphene layer or on the plurality of graphene layers deposited one on top of the other, in turn, an hBN layer can be deposited which is, for example, 3 nm thick.

Figure list

• 1 schematisch einen CVD-Reaktor 1 mit einem zugehörigen Gasmischsystem und
• 2 den Ausschnitt II in 1.

An exemplary embodiment of the invention is explained below with reference to the accompanying drawings. Show it:

• 1 schematically a CVD reactor 1 with an associated gas mixing system and
• 2 the section II in 1 .

Description of the embodiments

The figures show a CVD reactor 1 , which has a gas-tight housing and in which there is a gas inlet element 2 is located. Below the gas inlet element 2 there is a process chamber 3 whose bottom is a susceptor 5 forms, which can consist of graphite or coated graphite. The susceptor can be seen from below 5 by means of a heating device 6th be heated. The heating device can be an IR heater or an RF heater. Around the susceptor, which has a circular plan 5 a gas outlet member extends 7th , to which a vacuum pump, not shown, is connected.

The one to the process chamber 3 facing top of the susceptor 5 has a support surface 15th on which a substrate 4th rests, which can consist of sapphire, silicon, a metal or the like.

The gas inlet organ 2 has the shape of a shower head. Inside the gas inlet organ 2 is located between a gas outlet plate 9 and an intermediate plate 23 a cooling chamber 8th . Above the cooling chamber 8th is located between the intermediate plate 23 and an intermediate plate 13th a gas distribution chamber 21st . Between the intermediate plate 13th and a ceiling plate 16 there is another gas distribution chamber 11 .

In the gas distribution chamber 21st opens a feed line 20th into which gas can be fed from outside the CVD reactor. In the gas distribution chamber 11 opens a feed line 10 in from outside the CVD reactor 1 Gas can be fed.

The gas distribution chamber 11 is by means of a multitude of evenly over the gas outlet surface 25th the gas outlet plate 9 distributed tubes 12th with the gas distribution chamber 11 connected. The tubes 12th open into a gas outlet opening 14th through which the into the gas distribution chamber 11 fed gas into the process chamber 3 can flow in.

The gas distribution chamber 21st is by means of a large number of tubes 12th , 12 ' with the gas outlet area 25th connected so that through the the tube 12th , 12 ' associated gas outlet openings 24 one into the gas distribution chamber 21st fed gas can enter the process chamber.

In the cooling chamber 8th opens a feed line 8th' through which a coolant enters the cooling chamber 8th can be fed. The coolant can flow out of the cooling chamber again from the discharge line 8 " 8th flow out.

The reference number 19th denotes a pyrometer, with which the surface of the substrate 4th can be observed during growth in order to determine the surface temperature. The optical beam path 18th of the pyrometer 19th runs through a for the wavelength of the pyrometer 19th transparent window 17th in the ceiling plate 16 and through one of the tubes 12 ' .

The gas mixing system 29 has a controller, which can be a control computer. With the controller 29 can use different mass flow controllers 30th , 30 ' ; 37 , 37 ' ; 41 , 41 ' can be controlled. With the controller 29 In addition, the temperature of a temperature control bath can be set in which there is a source 32 , 32 ' of a liquid or solid starting material, called a bubbler 32 , 32 ' is trained. The reference number 31 , 31 ' refers to a concentration measuring device with which the concentration of the vapor within a carrier gas flow can be determined. With the reference number 39 , 39 ' denotes an inert gas source which makes an inert gas, for example a noble gas, available. The reference numbers 40 , 40 ' denote sources of a reactive gas, for example methane or another hydrocarbon.

The reference numbers 33 , 33 ' denote switching valves with which one in the bubblers 32 , 32 ' generated steam transported by a carrier gas either in a vent line 35 at the CVD reactor 1 bypassed or by a run line 34 , 34 ' into one of the supply lines 10 , 20th can be fed.

With the bubblers 32 , 32 ' reactive gases can be generated. For this purpose, from the inert gas source 39 , 39 ' an inert gas via the mass flow controller 30th , 30 ' into the bubbler 32 , 32 ' fed in. With the concentration meter 31 , 31 ' the vapor concentration in the carrier gas flow can be measured downstream. Before the reactive gas is fed into the gas inlet element 2 gets the reactive gas into the vent line 35 passed until a gas flow has stabilized. To start the deposition of a two-dimensional layer, the toggle switch 33 , 33 ' switched so that the stabilized gas flow through the run-line 34 , 34 ' into one of the gas distribution chambers 11 , 21st can be fed. In the exemplary embodiment, two sources are shown, with each of which a reactive gas can be generated from a powder or from a liquid. Several such sources can be provided in exemplary embodiments that are not shown.

Used in one of the gas distribution chambers 11 , 21st no reactive gas is fed in, so can via the valve 36, 36 'and the mass flow controller 37 , 37 ' an inert gas from the inert gas source 39 into the gas distribution chamber 11 , 21st be fed in.

Alternatively, a starting material available in gaseous form, for example methane or another hydrocarbon from a gas source, can also be used 40 , 40 ' be taken, and by means of the mass flow controller 41 , 41 ' into the gas distribution chamber 11 , 21st be fed in. Borazine can, if it is available above the boiling point, be provided with a gas source. Otherwise, Borazin can use a bubbler 32 , 32 ' to provide.

In order to deposit multilayer structures, one of the gas distribution chambers is alternated 11 , 21st a reactive gas or a mixture of two reactive gases and into the other of the gas distribution chambers 11 , 21st fed an inert gas. For example, by switching between a borazine flow and a methane flow, a multilayer structure made of hBN and graphene can be deposited. A graphene layer or a multiplicity of graphene layers can be embedded between two hBN layers, in particular monolayer layers.

Alternatively, a process gas, which is a Mixture of two reactive gases is to be fed. For example, one of the reactive gases can be tungsten-hexacarbonyl, which is supplied via a bubbler 32 , 32 ' can be made available. The other reactive gas can be a sulfur-tellurium or selenium compound.

The invention relates to all material pairings in the DE 10 2013 111 791 A1 are named. For this purpose, the disclosure content of this document is included in its entirety in this application.

The above explanations serve to explain the inventions covered by the application as a whole, which also develop the state of the art independently at least through the following combinations of features, whereby two, more or all of these combinations of features can also be combined, namely:

A method, which is characterized in that the gas inlet member 2 at least two separate gas distribution chambers 11 , 21st has, each with a lead 10 , 20th are fed with mutually different gases or gas mixtures, which simultaneously from the mutually different, each associated with one of the gas distribution chambers 11, 21 gas outlet openings 14th , 24 step out.

A use, which is characterized in that the gas inlet element 2 at least two separate gas distribution chambers 11 , 21st has, each with a lead 10 , 20th with mutually different gases or gas mixtures are fed, which simultaneously from the mutually different, each one of the gas distribution chambers 11 , 21st associated gas outlet openings 14th , 24 step out.

A method or a use, which is characterized in that in a first 11 of the gas distribution chambers 11 , 21st an inert gas and in a second 21 of the gas distribution chambers 11 , 21st a reactive gas is fed in, which reactive gas is in the process chamber 3 is decomposed pyrolytically, the decomposition products forming a two-dimensional layer, or that in the gas distribution chambers 11 , 21st Reactive gases different from one another are fed into the process chamber 3 react chemically with each other and form a two-dimensional layer.

A method or a use, which is characterized in that, in a second step, on a first two-dimensional layer deposited in a first step, when it is deposited through the first gas distribution chamber 11 and the gas outlet openings assigned to it 14th an inert gas and through the second gas distribution chamber 21st and the gas outlet openings assigned to it 24 a first reactive gas is fed into the process chamber, a second two-dimensional layer is deposited, during the deposition of which by the first gas distribution chamber 1 and the gas outlet openings assigned to it 14th a second reactive gas is fed that is different from the first reactive gas, and through the second gas distribution chamber 21st and the gas outlet openings assigned to it 24 an inert gas is fed into the process chamber, it being provided in particular that the two steps are repeated one or more times.

A method or a use, which is characterized in that two-dimensional layers different from one another are deposited on one another in several successive steps, the reactive gases used in particular alternating in different gas distribution chambers 11 , 21st be fed in.

A device which is characterized in that the gas inlet member 2 two separate gas distribution chambers 11 , 21st with one feed line each 10 , 20th having each of the two feed lines 10 , 20th can optionally be flow-connected to an inert gas source or to one of the reactive gas sources.

A method, a use or a device, which is characterized by a switching device 33 , 33 ' ; 37 , 37 ' ; 38, 38 ', with which either or alternately the inert gas source 39 , 39 ' or one of the reactive gas sources 32 , 32 ' ; 40 , 40 ' with a gas distribution chamber 11 , 21st can be brought into a flow connection.

A method, a use or a device, which is characterized in that the reactive gas sources 32 , 32 ' alternatively or alternately with a vent line 35 , by means of which the reactive gases at the process chamber 3 be bypassed, or with a run line 34 , 34 ' are connectable, with which the reactive gases in the process chamber 3 can be initiated. supplies a gas or a gas mixture which is deposited on the substrate 4th grows up as a two-dimensional layer.

A method, a use or a device, which is characterized in that the gas inlet element 2 a showerhead with a gas outlet surface 25th , in which the gas outlet openings 14th , 24 are arranged is, in which two by an intermediate plate 13th separate gas distribution chambers 11 , 21st are arranged, each with tubes 12th , 12 ' with the evenly over the gas outlet surface 25th distributed gas outlet openings 14th , 24 are flow-connected and / or that the material of the two-dimensional layer is graphene, hBN, or a transition metal dichalcogenide, in particular MoS ₂ , WS ₂ , MoSe ₂ or WSe ₂ and / or that the reactive gas is a carbon compound or borazine and / or that a first reactive gas is an element of a transition metal and is in particular a molybdenum compound or a tungsten compound, and that a second reactive gas contains an element of main group III and in particular is a sulfur compound, for example di-tert-butyl sulfide, a selenium compound or a tellurium compound and / or that the inert gas is a noble gas.

All the features disclosed are essential to the invention (individually, but also in combination with one another). The disclosure of the application hereby also includes the full content of the disclosure content of the associated / attached priority documents (copy of the previous application), also for the purpose of including features of these documents in the claims of the present application. The subclaims characterize, even without the features of a referenced claim, with their features independent inventive developments of the prior art, in particular in order to make divisional applications on the basis of these claims. The invention specified in each claim can additionally have one or more of the features provided in the above description, in particular provided with reference numbers and / or specified in the list of reference numbers. The invention also relates to design forms in which some of the features mentioned in the above description are not implemented, in particular insofar as they are recognizable for the respective purpose or can be replaced by other technically equivalent means.

List of reference symbols

1

CVD reactor

2

Gas inlet element

3

Process chamber

4th

Substrate

5

Susceptor

6th

Heating device

7th

Gas outlet member

8th

Cooling chamber

8th'

Supply line

8th''

Derivation

9

Gas outlet plate

10

Supply line

11

Gas distribution chamber

12th

pipe

12 '

pipe

13th

Intermediate plate

14th

Gas outlet opening

15th

Support surface

16

Ceiling plate

17th

window

18th

Beam path

19th

optical device, pyrometer

20th

Supply line

21

Gas distribution chamber

23

Intermediate plate

24

Gas outlet opening

25th

Gas outlet surface

29

control

30th

Mass flow controller

30 '

Mass flow controller

31

Concentration meter

31 '

Concentration meter

32

Bubbler

32 '

Bubbler

33

Changeover valve

33 '

Changeover valve

34

Run line

34 '

Run line

35

Vent line

37

Mass flow controller

37 '

Mass flow controller

39

Inert gas source

39 '

Inert gas source

40

Reactive gas source

40 '

Reactive gas source

41

Mass flow controller

41 '

Mass flow controller

TP

Process temperature

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102013111791 A1 [0004, 0026]
• WO 2017/029470 A1 [0004]
• DE 102011056589 A1 [0004]
• DE 102010016471 A1 [0004]
• DE 102004007984 A1 [0004]
• WO 2014/066100 A1 [0005]
• US 2010119727 [0006]
• DE 102013101534 A1 [0009]
• DE 102009043840 A1 [0009]
• DE 102007026349 A1 [0009]

Claims (10)

Method for depositing a two-dimensional layer on a substrate (4) in a CVD reactor (1), in which a process gas is fed into a gas distribution chamber (11, 21) of a gas inlet element (2) by means of a feed line (10, 20), which Has gas outlet openings (14, 24) which open into a process chamber (3) in which the process gas or decomposition products of the process gas in the process chamber (3) are brought to a surface of a substrate (4), and in which the substrate (4) _{is brought to a process temperature (T P} ) by means of a heating device (6) so that the process gas in the process chamber reacts chemically in such a way that the two-dimensional layer is deposited on the surface, characterized in that the gas inlet element (2) has at least two separate gas distribution chambers (11, 21), which are each fed with a supply line (10, 20) with mutually different gases or gas mixtures, which simultaneously from the vonei nander different gas outlet openings (14, 24) each assigned to one of the gas distribution chambers (11, 21) emerge. Use of a CVD reactor (1) for depositing a two-dimensional layer on a substrate (4), which has a gas inlet element (2) with a supply line (10, 20) opening into a gas distribution chamber (11, 21), a process chamber (3), in the gas outlet openings (14, 24) of the gas distribution chambers (11, 21) open out, and have a susceptor (5), which can be heated by a heating device (6), for receiving the substrate (4), a process gas entering through the feed line (10, 20) the gas inlet element (2), through the gas outlet openings (14, 24), is brought into the process chamber (3), where it reacts chemically in such a way that the two-dimensional layer is deposited on the surface, characterized in that the gas inlet element (2) is two of each other has separate gas distribution chambers (11, 21), each of which is fed with a supply line (10, 20) with gases or gas mixtures different from one another, which simultaneously from the different one of the gas distribution chambers (11, 21) associated gas outlet openings (14, 24) emerge. Procedure according to Claim 1 or use after Claim 2 , characterized in that an inert gas is fed into a first (11) of the gas distribution chambers (11, 21) and a reactive gas is fed into a second (21) of the gas distribution chambers (11, 21), which reactive gas is pyrolytic in the process chamber (3) is decomposed, the decomposition products forming a two-dimensional layer, or that mutually different reactive gases are fed into the gas distribution chambers (11, 21), which react chemically with one another in the process chamber (3) and form a two-dimensional layer. Method or use according to one of the preceding claims, characterized in that, in a second step, an inert gas is applied to a first two-dimensional layer deposited in a first step, and when it is deposited through the first gas distribution chamber (11) and the gas outlet openings (14) assigned to it the second gas distribution chamber (21) and the gas outlet openings (24) assigned to it, a first reactive gas is fed into the process chamber, a second two-dimensional layer is deposited, during the deposition of which through the first gas distribution chamber (1) and the gas outlet openings (14) assigned to it A second reactive gas is fed in that is different from the first reactive gas, and an inert gas is fed into the process chamber through the second gas distribution chamber (21) and the gas outlet openings (24) assigned to it, it being provided in particular that the two steps are carried out one or more times be repeated. Method or use according to one of the preceding claims, characterized in that two-dimensional layers different from one another are deposited on one another in several successive steps, the reactive gases used in particular being fed alternately into different gas distribution chambers (11, 21). Device for depositing a two-dimensional layer on a substrate (4) with a CVD reactor (1) which has a gas inlet element (2) with a supply line (10, 20) opening into a gas distribution chamber (11, 21), a process chamber (3), open into the gas outlet openings (14) of the gas distribution chambers (11, 21) and have a susceptor (5) which can be heated by a heating device (6) for receiving the substrate (4), the feed line (10, 20) being connected to a gas mixing system is, in which at least one inert gas source (39, 39 ') an inert gas and one or more reactive gas sources (32, 32'; 40, 40 ') are each provided at least one reactive gas, the reactive gas or a mixture of at least two reactive gases have the property, brought into the heated process chamber (3), to react chemically in such a way that a two-dimensional layer is deposited on the substrate (4), are provided, characterized in that the gas inlet element (2) two i separate from each other Has gas distribution chambers (11, 21) each with a feed line (10, 20), each of the two feed lines (10, 20) being optionally flow-connectable to an inert gas source or to one of the reactive gas sources. Method or use according to one of the preceding claims or device according to Claim 6 , characterized by a switching device (33, 33 '; 37, 37'; 38, 38 '), with which the inert gas source (39, 39') or one of the reactive gas sources (32, 32 '; 40, 40') can be selected or alternately can be brought into a flow connection with a gas distribution chamber (11, 21). Method, use or device according to one of the preceding claims, characterized in that the reactive gas sources (32, 32 ') optionally or alternately with a vent line (35), by means of which the reactive gases are conducted past the process chamber (3), or with a run line (34, 34 ') can be connected, with which the reactive gases can be introduced into the process chamber (3). supplies a gas or a gas mixture which grows on the substrate (4) as a two-dimensional layer. Method, use or device according to one of the preceding claims, characterized in that the gas inlet element (2) is a showerhead with a gas outlet surface (25), in which the gas outlet openings (14, 24) are arranged, in which two through an intermediate plate (13) separate gas distribution chambers (11, 21) are arranged, each of which is in flow communication with tubes (12, 12 ') with the gas outlet openings (14, 24) evenly distributed over the gas outlet surface (25) and / or that the material of the two-dimensional layer graphene, hBN, or a transition metal dichalcogenide, in particular MoS ₂ , WS ₂ , MoSe ₂ or WSe ₂ and / or that the reactive gas is a carbon compound or borazine and / or that a first reactive gas is an element of a Is transition metal and is in particular a molybdenum compound or a tungsten compound, and that a second reactive gas contains an element of main group III and in particular is a sulfur compound, for example di-tert-butyl sulfide, a selenium compound or a tellurium compound and / or that the inert gas is a noble gas. Method, use or device, characterized by one or more of the characterizing features of one of the preceding claims.

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